This invention relates to poly(arylene ether) polymers, and more particularly to grafting olefinic functional groups to the backbone of poly(arylene ether) polymers to provide cross-linkable polymers having particular utility as coatings and adhesives with high glass transition temperatures and low moisture uptake.
The electronics industry has recently sought low dielectric materials for use in fabricating very fine dimensioned integrated circuits. However, the need for materials compatibility and dimensional stability over a wide range of conditions not only during ultimate end use, but also during further processing conditions leading to the finished integrated circuits, has presented a significant problem. The problem has been to make a polymeric thermoset system. This problem has been a very difficult one to solve, particularly for high Tg polymers where the desired temperature for reaction (i.e., cure) is below 450xc2x0 C. and more preferably below 200xc2x0 C.
Therefore, there is a need in the electronic fabrication industry for the replacement of silica-based, interlayer dielectric materials with materials of lower dielectric values. Silica and its modified versions have dielectric values on the order of 3.0 to 5.0 and usually 4.0 to 4.5. Polymeric materials used as replacements for silica as interlayer dielectric materials can have dielectric constant values in the range of 1.9 to 3.5, which values are highly dependent on the structure of the polymeric materials. To successfully replace silica as an interlayer dielectric material, the properties of polymeric materials must conform to the rigid manufacturing requirements for integrated circuits or microchips in the electronic fabrication industry. Crosslinking has been recognized as one way to address the requirements of electronic materials polymers.
Past attempts utilized various different approaches for crosslinking polymers. A detailed summary of these attempts is provided in the inventor""s U.S. Pat. No. 6,060,170, assigned to Air Products and Chemicals, Inc. The document itself teaches use of poly(arylene ether) polymer compositions having aromatic groups grafted on the poly(arylene ether) backbone, which grafts allow for crosslinking of the polymers in a temperature range of 200 to 450xc2x0 C. A further reduction in crosslinking temperature would, however, be desirable.
U.S. Pat. Nos. 5,179,188 and 5,114,780 to Mercer et al. also disclose poly(arylene ether)-based polymers. These patents teach that fluorinating the backbone of such polymers provides a dielectric material with superior properties. However, the use of fluorinated arylene groups in the backbone of the polymer introduces functional reactive groups, which in turn deteriorate insulating and moisture adsorption properties.
Integrated circuit and chip manufacturing require suitable coatings and adhesives, especially die-attach adhesives. These adhesives are required to have low dielectric constants. In addition, it is desired to provide these die-attach adhesives with unlimited storage stability at 25xc2x0 C., storage stability at 40xc2x0 C. sufficient to weather transportation in non-refrigerated vehicles, and cure temperatures of 170 to 190xc2x0 C. within 1 to 2 hours. After cure, it is desired to have a Tg in the range of 160 to 180xc2x0 C., a dielectric constant below 2.7 with frequency independence, and a maximum moisture absorption of less than 0.17 wt %.
All references cited herein are incorporated herein by reference in their entireties.
Accordingly, the invention provides a poly(arylene ether) polymer including polymer repeat units of the following structure:
xe2x80x94(Oxe2x80x94Ar1xe2x80x94Oxe2x80x94Ar2xe2x80x94)mxe2x80x94(Oxe2x80x94Ar3xe2x80x94Oxe2x80x94Ar4xe2x80x94)nxe2x80x94
where Ar1, Ar2, Ar3, and Ar4 are identical or different aryl radicals, m is 0 to 1, n is 1-m, and at least one of the aryl radicals is grafted to at least one unsaturated group that is non-aromatic and is adapted to crosslink at a curing temperature below 200xc2x0 C. without producing volatiles during curing and without providing functional groups after curing.
Also provided is a composition comprising the polymer, and optionally, a diluent, which does not afford a functional group or interfere with the mechanical or electrical properties of the composition.
Still further provided is a method for providing a substrate with a film having a Tg from 160xc2x0 C. to 180xc2x0 C., a dielectric constant below 2.7 with frequency independence, and a maximum moisture absorption of less than 0.17 wt %, the method comprising applying the polymer of the invention to the substrate and heating the polymer to a curing temperature below 200xc2x0 C.